​Selatan Strait (South Strait), also known as Penang Strait and "South Channel",is the channel that separates Penang Island from mainland Peninsular Malaysia. The mainland side, known as Seberang Perai, forms the strait's eastern side, while the east coast of Penang Island forms its western side. The north and south ends of the strait join the Strait of Malacca, the world's busiest sea route.

There are a few islands and islets in the channel. The biggest is Jerejak, a former leper colony that is now in the process of being developed into a tourist destination.

The strait is bridged by Penang Bridge, the longest bridge in Southeast Asia. To ease congestion, construction of the Penang Second Bridge began in 2008 as part of the Ninth Malaysia Plan.

Penang Port is the oldest and longest established port in Malaysia. The port serves as the main gateway for shippers in the northern states of Malaysia and also the southern provinces of Thailand. The port is strategically located along the Straits of Malacca, one of the busiest shipping routes in the world. Penang Port is fully equipped to handle all types of cargo such as containers, liquid, dry bulk, break bulk and others; and provides a multitude of services to cater for their safe and efficient transit via the port’s various terminals and facilities.

Penang Ferry Service is the oldest ferry service in Malaysia. Located in the state of Penang, this famous ferry service connects Sultan Abdul Halim ferry terminal in Butterworth to Raja Tun Uda ferry terminal at Weld Quay in George Town in Penang Island. The ferries are designed for vehicles to roll-on/roll-off. Some board pedestrian passengers on the upper deck and small vehicles (cars) on the lower deck, whereas some board vehicles on both decks. The benches for passengers on the upper decks have pivoting backs that can be flipped back and forth so passengers can sit facing in the direction of travel regardless of which way the ferry is goi